Clam opener tools

ABSTRACT

A plier-like clam-opener tool having a variable pivot point to provide varying mechanical advantage as the tool is operated to slice a clam open.

United States Patent Scott et al. [451 Aug. 22, 1972 1 CLAM OPENER TOOLS[5 6] References Cited [72] Inventors: Merton E. Scott; Richard W.UNITED STATES PATENTS Sch 1 ''g; a figgfl f 2,445,480 7/1948 Gantt..146/13 ux an 3,091,841 6/1963 Wurzel ..81/416 X o 708,014 9/1902Blagden ..l7/75 [73] Assigneez Scott Machine Development Cor- Iporation, Walton, N.Y. FOREIGN PATENTS OR APPLICATIONS [22] Filed: Aug.3, 1970 1,207,064 8/1959 France ..17/75 [21] Appl' 60265 PrimaryExaminer-Lucie H. Laudenslager Attorney-Richard G. Stephens [52] US. Cl...l7/75, 81/416, 146/13 [51] Int. Cl ..A22c 29/00 57 ABSTRACT [58] Fieldof Search ..l7/75, 76; 146/13; 81/350,

1 81/351, 416 A plier-hke clam-opener tool having a variable pivot,

point to provide varying mechanical advantage asthe tool is operated toslice a clam open.

12 Claim, 11 Drawing Figures PATENTEDmczz I972 3.685.097 sum 3 OF 3MECHANICAL ADVANTAGE RATE OF TRAVEL WIDE FULLY OPEN CLOSED HANDLEMOVEMENT FIG. 6

CLAM OPENER TOOLS Clams and oysters and the like are commonly harvestedwith a variety of sizes, and automatic machinery which will open clamsand oysters is either unavailable or very expensive. Also, seafood itemsof this type ordinarily retain their taste and freshness better if theyare opened at individual restaurants or kitchens immediately prior toconsumption rather than being opened sometime before at a centralprocess plant. Clams and oysters are commonly opened at restaurants andclambakes using various hand tools, most commonly special forms ofknives. Opening clams rapidly and efficiently with knives and othertools available in the prior art ordinarily requires a person withstrong hands and a considerable degree of manual dexterity, and the workis tedious and tiring even to such a person having considerableexperience. Unskilled persons also sometimes accidentally cut themselveswith clam knives. The difficulty of opening clams and oysters is aprimary factor which limits wider consumption of such seafood items.

A variety of attempts have been made to provide tools which willsimplify the task, and some prior art attempts are shown in US. Pat.Nos. 708,014; 2,017,370; 2,609,565; 2,738,546 and Des. 196,381. Whilesome of the prior art devices may have achieved some substantial usagenone of them are believed to have gained widespread acceptance, and allof them suffer from at least one disadvantage which is overcome by thepresent invention.

While the two half-shells of a clam frequently appear to the casualobserver to be tightly sealed together around their entire periphery, itis well known that the two half-shells of a clam are actually heldtogether by a tough, fibrous hinge which is exposed and which extendsalong only a small portion of the periphery, and held at two otherplaces by powerful muscles which are inside the clam and not exposed.

Prior art clam-opener tools of the plier or lever type have generallyincluded a pair of levers pivotally affixed together, with a knife bladeend on one lever pivoting relative to a cup-shaped clam-retaining end onthe other lever, so that squeezing the two opposite or handle ends ofthe levers together advance the knife blade end through the clam towardthe cup-shaped clam-retaining end. The distance of the pivot point fromthe working ends of the two levers deten'nines the mechanical advantageof the tool. If the pivot point is situated too near the handle ends ofthe tool, the tool will have little mechanical advantage, or even anegative mechanical advantage, frequently making it very difficult orimpossible for one to squeeze the tool sufficiently hard to open theclam. While one theoretically can provide any desired mechanicaladvantage by making the two lever arms long enough, it will be apparentthat that offers no solution. The span of the human hand tends to limitthe usable lever arm length if the operator is to be capable of holdingthe tool with one hand while inserting the clam with the other. If, onthe other hand, the pivot point is situated quite near to the blade endof the tool, a large mechanical advantage may be obtained, making iteasy for one to apply sufficient force with one hand to open the clam.However, the greater the mechanical advantage provided by tool, thelesser will be the distance which the blade will travel for a givendistance of travel of the two handle ends toward each other, and thelesser will be the change in distance between the jaws betweenfullyopened and fully-closed conditions. Thus if the pivot point issituated near the blade end so as to provide suf' ficient mechanicaladvantage to open the clam easily, the restricted travel of the bladelimits the range of clam sizes on which the tool may be used. Because ofthat inherent characteristic of a lever, the clam openers of the priorart tend to be incapable of sufiiciently cutting a clam by one squeezeof the tool, with the result that the operator then often has had toopen the tool, rotate the half-severed clam to a different orientationrelative to the blade and then to squeeze the tool again. Not only aretwo (or sometimes more) such operations required, thereby greatlydecreasing operator speed, but rotation of the partially-severed clamsin the tool has required the operator to use his other hand toaccomplish the rotation, rather than allowing him to use it to locateopened clams on a tray or bed of ice and to reach for the next clam. Itis a primary object of the present invention to provide an improvedplier-like opener tool which overcomes those disadvantages of prior arttools.

The prior art clam knives and plier-like clam tools of the prior art,all are designed to cut the two interior muscles of the clam in order toopen the clam, since the two interior muscles are formed by a softmeat-type material which is far easier to sever than the hinge. Priorart clam tools of the plier-type have not attempted to sever the clamhinge, since the great meehenical advantage required would severelyrestrict the range of clam sizes with which they could be used. Becausethe two muscles lie wholly inside the clam, the severing blades of priorart tools have been required to separate the shells against the strengthof the muscles before the muscles can be cut. The edges of the clamshells are ordinarily much thicker at and adjacent the hinge than aroundthe remainder of the periphery. When prior art blades have been insertedbetween the thinner edges of a pair of shells in order to cut themuscles, it has been difficult to align such blades so as to avoidbreaking the edges of the shells. Also, nature doe not always cause thejoint between such edges to be straight, so that forcing a straightblade edge between the shells sometimes chips or breaks the shells. Thedisadvantages of chipping the shells and mixing shell chips with theclam meat are obvious.

The tool of the present invention employs a new technique for openingclams. Rather than inserting a blade into the clam through the thinneredges of the shell in order to cut the interior muscles, the presentinvention severs through the tough, fibrous exposed hinge, and throughone interior muscle, which allows the clam then to be easily opened withones fingers against the force of the remaining muscle. The severingprocess begins at the easily-accessible exposed hinge portion of theclam, where the shell is thickest and strongest, so that shell breakageoccurs less often, and severing of the hinge occurs without any priorseparation of the two shells.

Because the tool of the present invention cuts directly through thetough hinge muscle, considerable mechanical advantage is required, andin order to provide sufficient mechanical advantage one might assumethat the range of blade travel, and hence range of clam sizes with whichthe tool could be used, would be drastically limited. However, inaccordance with one important feature of the invention, an automaticvariation in the location of the pivot point is provided. A largemechanical advantage is provided during the initial portion of jawclosure as the hinge is severed, but then the pivot point shifts toprovide less mechanical advantage and greater blade travel as the blademoves into the clam to sever an internal muscle. Such variation in thetool pivot point allows the jaws of the tool to move sufficiently toaccept a wide variety of clam sizes.

A central concept of the present invention involves the use of a pliercutter having a varying pivot point about which the two arms of the toolpivot, to provide large mechanical advantage during an initial portionof a cutting stroke when the hinge is being cut, and thereafter toprovide a decreased mechanical advantage and greater knife travel duringa remaining portion of a cutting stroke, so that the softer interiormuscle will be reached and severed.

A further important feature is that the mechanical advantage of the toolchanges in the desired sense automatically as the operator squeezes thetool, without any need for the operator to reset the tool on the clam,or to perform any adjustment to the tool, or to use more than one hand.

Other objects of the invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the features of construction,combination of elements, and arrangement of parts, which will beexemplified in the constructions hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

For a fuller understanding of the nature and objects of the inventionreference should be had to the following detailed description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a side view of one embodiment of the invention shown with thejaws of the tool fully opened.

FIG. 1a is an opposite-side view of a portion of the tool.

FIG. 2 is side view of the tool of FIG. 1 corresponding to the view ofFIG. 1 but with the jaws of the tool shown partially closed.

FIG. 3 is a side view of the tool corresponding to the views of FIGS. 1and 2 but with the jaws shown fully closed.

FIG. 4 is a plan view of the tool taken at lines 4-4 in FIG. 3.

FIG. 5 is an end section view of the tool taken at lines 5-5 in FIG. 3.

FIG. 6 is a graph useful in understanding the operation of the tool ofFIGS. 1-5.

FIG. 7 is an isometric view of some alternative form of the invention.

FIG. 8 a view corresponding to FIG. la but showing one optionalmodification of the tool.

FIG. 9 is a side view of portions of an alternative form of theinvention.

FIG. 10 is a side view of portions of a further altemative embodiment ofthe invention.

Referring now to the FIGURES, and in particular FIGS. l5, the tool willbe seen to comprise a first rigid arm 11 having a handle end 110 and aknife blade end 1117. A cylindrical pivot pin 12 is fixedly mounted orstaked in a hole in arm 11 to extend from a flattened surface portion 11c on arm 11 generally near blade end 11b. Knife blade end 11b, as shownin FIG. 5 preferably is provided with a wedge-shaped cross-section, withits inner side arranged perpendicularly to the axis x-x of pin 12 andits outer side arranged at an acute angle (shown as a) relative to theinner side. The rear portion of flattened inner face 11c of arm 11terminates at an inwardly-extending or widened portion of arm 11 shapedto provide a rounded cam surface 18 (FIGS. 1 and 4). The tool alsoincludes a second rigid arm 13 having handle 1313a and a widened clamseat end 13b. A flattened surface portion (FIG. 1a) on the inner side ofam l3-includes an arcuate slot 14 through arm 13 within which pin 12 issituated. A flat washer 15 is shown held on pin 12 by means of a screwwhich threads into pin 12, thereby fastening the two arms pivotallytogether so that the flattened surfaces 110, 13c of the two armsslidingly abut each other. If desired, the end of pin 12 may be widenedby flattening so that no screw is necessary. Flattened inner face 130 ofarm 13 terminates at its forward end by an abrupt widening of arm 13,thereby providing a widened, generally circular, and preferably slightlyhollowed or spoon-shaped surface at 13D. Hollowing outsurface 13d allowsa clam to seat more securely, of course. When the tool is opened, i.e.handle ends 110, 13a are spread apart, point on arm 11 eventuallystrikes end 132 of surface 13d, as shown in FIG. la, and with pin 12then located in one end of slot 14, further opening of the tool isprevented.

A clam is inserted on rounded surface or seat 13d of end 13b when thejaws are substantially open to approximately the position shown inFIG. 1. Pivot pin 12 is then located at end (FIG. 3) of arcuate slot 14.As the handle ends 11a, 130 are squeezed together, from the positionshown in FIG. 1 to that shown in FIG. 2, the knife blade tip 11d rotatesaround the pin 12 axis at the upper end 14a of slot 14, describing apath shown by dashed line in 17 in FIG. 1. The mechanical advantage ofthe tool is then determined by, and is proportional to, the ratio ofdimension d to dimension 0 in FIG. 1 assuming that operator force isapplied at arrow F in FIG. 1. The clam (not shown) is angularly orientedrelative to seat 13d so that path 17 of blade end 11d and the path ofblade portions inwardly therefrom will pass through the tough, fibroushinge of the clam. During this portion of the operation, between theconditions shown in FIG. 1 and FIG. 2, the knife blade severs the clamhinge, and maximum mechanical advantage is provided. The displacement ofthe knife blade relative to the clam and arm 13 per degree of rotationof the handles about the pivot point is directly proportional to thelever arm distance a, of course, and under such conditions suchdisplacement is minimum. The manner in which the mechanical advantageand rate of travel of the blade vary as the handles are moved from afully open condition to a fully closed condition is shown graphically inFIG. 6. The abscissa value 2 in FIG. 6 represents the condition shown inFIG. 2, wherein a step decrease in mechanical advantage occurs and astep increase in rate of travel occurs as point f of arm 13 engagespoint f of cam surface 18 on arm 11.

When the tool arrives at the condition shown in FIG. 2 the hinge will becompletely or substantially severed and much less force is required tosever one of the interior muscles. In FIG. 2 point f on arm 13 is shownjust striking point f on cam surface 18 of arm 11. As the handles 11a,13a are squeezed further together, points g and h on arm 13 successivelyengage points g and h respectively, on cam surface 18 of arm 11, and pin12 rides upwardly in arcuate slot 14. The edge between points f and h onarm 13 will be seen to act as a cam follower which rolls along camsurface 18 as pin 12 slides in slot 14. When the tool is advanced to thecondition shown in FIG. 2 and rotation of arm 11 relative to 13 beginsabout point f on arm 13, it will be seen that the mechanical advantageof the tool will suddenly be pro portional to the ratio of dimension eto dimension b rather than to the ratio of dimension d to dimension a astheretofore. As further closure of the tool causes points g and h on arm11 to successively engage points g and h on arm 13, so that arm 11rotates about pivot points which are successively located morerearwardly on arm 13, it will be seen that the mechanical advantage ofthe tool gradually further decreases, until the tool is fully closed asshown in FIG. 3. At the instant of full closure the mechanical advantagewill have become proportional to the ratio of dimension f to dimension cin FIG. 3. As the mechanical advantage decreases, the amount of bladetravel through the clam per degree of tool handle closure increases, sothat the blade cuts through considerably more of the clam during thelast portions of a cutting stroke than if the mechanical advantage hadremained unchanged. The manner in which the mechanical advantage andrate of travel vary between the conditions shown in FIGS. 2 and 3 isgraphically indicated between abscissa numerals 2 and 3 in FIG. 6. Whenthe tool has fully closed it will have completely severed the hinge andall or most of one of the interior muscles. The clam then may be spreadapart very easily with ones fingers against the force of the remaininginterior muscle. Provision of a spoon shape on end 13b facilitatesremoval of clam meat from an opened half-shell.

It is desirable that closure of the tool be limited so that blade tip 11d will not be blunted or dulled by striking clam seat 13b. Closure maybe limited either by shaping arms 11 and 13 so that handle ends 11a, 13astrike each other slightly before tip 11d can engage seat 13b, or bylimiting the length of arcuate slot 14, so that pin 12 seats against end14c of slot 14 slightly before tip 11d can strike seat 13b, andobviously both such limiting means may be used if desired.

The alternative embodiment of the invention shown in FIG. 7 operatesaccording to the same principles as the previous embodiment. However,cam block 18', which corresponds principle to cam surface 18 of theprior embodiment, is made adjustable in position along arm 11, so thatthe point of tool closure at which rate of travel is increased can beadjusted. Cam block 18' may be adjusted along slot 20 by loosening screw21, which holds block 18' on arm 11 with a nut (not shown). The screw 21passes through block 18 at a distance from the center of block 18, whichis shown having the shape of an equilateral triangle. By rotatablyadjusting block 18 as well as longitudinally adjusting its positionalong arm 11, it will be seen that one can vary the magnitude of thestep increase in rate of blade travel as well as varying the point atwhich the increase occurs when closure of the tool causes arm 13 tostrike a corner of block 18'. If block 18' is given straight sides asshown, it will be seen that a single step increase of blade travel willoccur during closure. One or more sides of block 18' may be curved, ifdesired, to provide cam surfaces similar to that of cam surface 18 inFIG. 1, so that a gradual increase in blade travel rate will occur afterthe initial step increase, in the manner of FIGS. l-6.

Opening of a batch of clams or oysters is made slightly easier if thetool will automatically open to a maximum width that is slightly largerthan the largest of the clams or oysters to be opened, rather thanopening twice as far as is necessary in order to insert the clam betweenthe jaws, for example. A fixed stop such as Be in FIG. la, if built toallow jaw opening to accommodate large diameter oysters, will allow muchmore jaw opening than is necessary for small clams, for example. In FIG.8 the maximum amount which the jaws will open is made adjustable, bymeans of adjustment screw l3e', which is locked in place by means of nut22.

It will be apparent that the positions of blade portion 11d and clamportion 13d can be interchanged in any embodiment of the invention withno difference in the operation, i.e., the blade could be fashioned onone end of the arm having the slot and the seat could be provided on theend of the arm carrying the pivot pin and the cam means.

In the device of FIG. 9 a bolt 26 passes through a round hole in arm 11and through a straight slot 24 in arm 13, and secures the arms together.The head of the bolt and the nut on the end of the bolt are not shown inFIG. 9. A pad 25 formed on arm 13 provides an edge having corners 25aand 25b. When bolt 26 is at the upper end of slot 24 as shown in FIG. 9,comer 25a limits the amount which the tool can be opened. When a clam isplaced between the jaws and the handles squeezed, the initial rotationoccurs about bolt 26 in the position shown. Eventually corner 25b of pad25 engages the edge of arm 11 at point j, and the pivot point is therebysuddenly shifted rearwardly to corner 25b. As the handles are squeezedfurther together, comer 25b then rides along the edge of arm 11 towardpoint k, while bolt 26 slides downwardly and leftwardly in slot 24.While the pivot point remains at comer 25b, the blade travel ratecontinues to gradually increase, since movement of bolt 26 in slot 24moves arm 1 l forwardly, thereby increasing the lever arm distancebetween blade tip 11d and pivot point 25b. Eventually the pivoting aboutcomer 25b causes the force between bolt 26 and slot 24 to act normal tothe side of slot 24, preventing further closing of the tool and furtherforward motion of arm 11 relative to arm 13, so that no further stopmeans is required to prevent blade tip 11d from blunting on the seat. Astop may be provided instead, either by forming the handle ends so thatthey meet, or by limiting the length of slot 24 so that bolt 26 reachesthe end of slot 24 at the desired limit position.

It should be apparent at this point that the cam surfaces shown areexemplary only, and that a wide variety of equivalent cammingarrangements may be substituted without departing from the invention.The cam surfaces need not act on an outside edge of one of the levermembers. In FIG. 10, for example, am 13 carries a pin 13f which extendsinto a hole 1 lfthrough arm 1 l, to provide equivalent operation to thatof surface 18 and the outer edge of arm 13 in FIGS. l-3.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained, andsince certain changes may be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

l. A tool for opening clams or oysters and the like, comprising, incombination: a first arm having a blade portion adjacent one of its endsand a handle portion adjacent its other end; a second arm having a seatportion adjacent one of its ends and a handle position adjacent itsother end; and pivot means interconnecting said arms to cause said bladeportion to advance toward said seat portion as said handle ends of saidarms are moved relative to each other, said pivot means providing apivot point which varies in position relative to at least one of saidarms as said handle ends of said arms are moved relative to each other,said pivot means comprising a slot in one of said arms, a first cammeans on said one of said arms, a pin carried by the other of said arms,and a second cam means on said other of said arms, said pin slidablyengaging said slot, and said first cam means being adapted to engagesaid second cam means when said handle ends of said arms have been movedto a predetermined position relative to each other.

2. A tool according to claim 1 wherein said pivot means interconnectingsaid arms is operable to automatically move said pivot point toward saidhandle ends of said arms as said arms are moved to advance said bladeportion toward said seat portion.

3. A tool according to claim 1 wherein said pivot means interconnectingsaid arms is operable to provide a step decrease in mechanical advantageas said arms are moved to advance said blade portion toward said seatportion.

4. A tool according to claim 1 wherein said pivot means interconnectingsaid arms is operable to provide a gradual decrease in mechanicaladvantage as said arms are moved to advance said blade portion towardsaid seat portion.

5. A tool according to claim 1 wherein said pivot means interconnectingsaid arms is operable to provide a step decrease in mechanical advantageas said arms are moved to advance said blade portion a first distancetoward said seat portion and operable to provide a gradual furtherdecrease in mechanical advantage as said arms are moved to advance saidseat portion a further distance toward said blade portion.

6. A tool according to claim 1 having adjustable stop means to limit themaximum distance which said blade portion may be moved away from saidseat portion.

7. A tool according to claim 2 in which one of said cam means rollsalong the other of said cam means and said pin slides along said slotwhen said handle ends of said arms are moved past said predeterminedposition to further advance said blade portion toward said seat Portion8. A tool according to clalm 2 m WhlCh a portion of one of said cammeans slides along the other of said cam means and said pin slides alongsaid slot when said handle ends of said arms are moved past saidpredeter mined position to further advance said blade portion towardsaid seat portion.

9. A tool according to claim 2 in which a given one of said armsincludes means for adjusting the position of its associated cam meansrelative to said given one of said arms.

10. A plier-like tool having a step change in mechanical advantage,comprising, in combination: firstand second rigid arms each having aworking end and a handle end, said first arm having a pin affixedthereto, said second arm having a slot therein, said pin engaging saidslot, said first and second arms having first and second cam means,respectively, said cam means being adapted to engage each other whensaid handle ends of said arms have been moved to a predetermined angularposition relative to each other, whereby, as said handle ends are movedtoward each other, said arms first rotate relative to each other aboutsaid pin until said cam means engage each other and then said armsrotate relative to each other about the point of engagement of said cammeans and said pin slides in said slot.

11. A tool according to claim 10 wherein said cam means are locatednearer the handle ends of their respective arms than said pin and slot,whereby a step decrease in mechanical advantage occurs as said cam meansengage each other.

12. A tool according to claim 10 wherein varying portions of at leastone of said cam means engage the other of said cam means after said armshave been moved past said predetermined angular position, whereby saidarms rotate relative to each other about said varying portions.

1. A tool for opening clams or oysters and the like, comprising, incombination: a first arm having a blade portion adjacent one of its endsand a handle portion adjacent its other end; a second arm having a seatportion adjacent one of its ends and a handle position adjacent itsother end; and pivot means interconnecting said arms to cause said bladeportion to advance toward said seat portion as said handle ends of saidarms are moved relative to each other, said pivot means providing apivot point which varies in position relative to at least one of saidarms as said handle ends of said arms are moved relative to each other,said pivot means comprising a slot in one of said arms, a first cammeans on said one of said arms, a pin carried by the other of said arms,and a second cam means on said other of said arms, said pin slidablyengaging said slot, and said first cam means being adapted to engagesaid second cam means when said handle ends of said arms have been movedto a predetermined position relative to each other.
 2. A tool accordingto claim 1 wherein said pivot means interconnecting said arms isoperable to automatically move said pivot point toward said handle endsof said arms as said arms are moved to advance said blade portion towardsaid seat portion.
 3. A tool according to claim 1 wherein said pivotmeans interconnecting said arms is operable to provide a step decreasein mechanical advantage as said arms are moved to advance said bladeportion toward said seat portion.
 4. A tool according to claim 1 whereinsaid pivot means interconnecting said arms is operable to provide agradual decrease in mechanical advantage as said arms are moved tOadvance said blade portion toward said seat portion.
 5. A tool accordingto claim 1 wherein said pivot means interconnecting said arms isoperable to provide a step decrease in mechanical advantage as said armsare moved to advance said blade portion a first distance toward saidseat portion and operable to provide a gradual further decrease inmechanical advantage as said arms are moved to advance said seat portiona further distance toward said blade portion.
 6. A tool according toclaim 1 having adjustable stop means to limit the maximum distance whichsaid blade portion may be moved away from said seat portion.
 7. A toolaccording to claim 2 in which one of said cam means rolls along theother of said cam means and said pin slides along said slot when saidhandle ends of said arms are moved past said predetermined position tofurther advance said blade portion toward said seat portion.
 8. A toolaccording to claim 2 in which a portion of one of said cam means slidesalong the other of said cam means and said pin slides along said slotwhen said handle ends of said arms are moved past said predeterminedposition to further advance said blade portion toward said seat portion.9. A tool according to claim 2 in which a given one of said armsincludes means for adjusting the position of its associated cam meansrelative to said given one of said arms.
 10. A plier-like tool having astep change in mechanical advantage, comprising, in combination: firstand second rigid arms each having a working end and a handle end, saidfirst arm having a pin affixed thereto, said second arm having a slottherein, said pin engaging said slot, said first and second arms havingfirst and second cam means, respectively, said cam means being adaptedto engage each other when said handle ends of said arms have been movedto a predetermined angular position relative to each other, whereby, assaid handle ends are moved toward each other, said arms first rotaterelative to each other about said pin until said cam means engage eachother and then said arms rotate relative to each other about the pointof engagement of said cam means and said pin slides in said slot.
 11. Atool according to claim 10 wherein said cam means are located nearer thehandle ends of their respective arms than said pin and slot, whereby astep decrease in mechanical advantage occurs as said cam means engageeach other.
 12. A tool according to claim 10 wherein varying portions ofat least one of said cam means engage the other of said cam means aftersaid arms have been moved past said predetermined angular position,whereby said arms rotate relative to each other about said varyingportions.